Subject: FahCore_a8 v0.0.12 segfault on Ubuntu 24.04 LTS / Kernel 6.14 - CPU work units crash immediately
System Information:
OS: Ubuntu 24.04 LTS
Kernel: 6.14
CPU: AMD Ryzen 9 5900X 12-Core Processor (24 threads)
GPU: NVIDIA GeForce RTX 5070 Ti
RAM: 62.72 GiB
F@H Client: v8.4.9
Username: Hemlok
Team: 250299
Problem Description:
All CPU work units fail immediately after starting with "Core was killed" / "Core crashed with exit code 0" errors. GPU folding works perfectly without issues.
Symptoms:
CPU work units (using FahCore_a8 v0.0.12, Gromacs core) consistently crash within seconds of starting
Work units complete only "1 out of 2500000 steps (0%)" before crashing
GPU work units (using Core22, OpenMM) complete successfully
Pattern repeats with every CPU work unit assigned
Example from F@H logs:
20:55:43:I1:WU185:Project: 16959 (Run 19, Clone 116, Gen 991)
20:55:43:I1:WU185:Calling: mdrun -c frame991.gro -s frame991.tpr -x frame991.xtc -cpt 5 -nt 12 -ntmpi 1
20:55:43:I1:WU185:Steps: first=-1817467296 total=-1814967296
20:55:44:I1:WU185:Completed 1 out of 2500000 steps (0%)
20:56:51:E :WU185:Core was killed
20:56:51:E :WU185:Core crashed with exit code 0
20:56:51:E :WU185:Core returned FAILED_1 (0)
20:56:51:E :WU185:Run did not produce any results. Dumping WU
```
**Note:** The negative step numbers (`first=-1817467296 total=-1814967296`) appear unusual and may indicate a corrupted work unit or core issue.
**Kernel logs (dmesg) show segmentation faults:**
```
[15374.949026] FahCore_a8[13727]: segfault at fffffffe2e338230 ip 000000000071b329 sp 000076475dffad70 error 5 in FahCore_a8[31b329,406000+e6d000] likely on CPU 15 (core 3, socket 0)
[15374.949036] Code: 6a 59 d1 c4 41 7a 2c cd c5 7a 2c c1 c5 fa 2c fa c4 c1 7a 2a c1 4d 63 d1 4c 8b 4c 24 30 c4 41 0a 2a f0 c5 12 5c e0 c5 f8 57 c0 <c4> 01 1a 58 2c 91 4d 63 c8 c5 fa 2a c7 4c 8b 44 24 38 c4 41 72 5c
[15493.242565] FahCore_a8[14043]: segfault at fffffffe17b866b0 ip 000000000071b329 sp 000072e7f6ffcd70 error 5 in FahCore_a8[31b329,406000+e6d000] likely on CPU 20 (core 10, socket 0)
[15493.242579] Code: 6a 59 d1 c4 41 7a 2c cd c5 7a 2c c1 c5 fa 2c fa c4 c1 7a 2a c1 4d 63 d1 4c 8b 4c 24 30 c4 41 0a 2a f0 c5 12 5c e0 c5 f8 57 c0 <c4> 01 1a 58 2c 91 4d 63 c8 c5 fa 2a c7 4c 8b 44 24 38 c4 41 72 5c
```
**FahCore_a8 details:**
```
Core: Gromacs
Type: 0xa8
Version: 0.0.12
Date: Jan 16 2021
Time: 19:24:44
Compiler: GNU 8.3.0
Platform: linux2 4.15.0-128-generic
Bits: 64
Mode: Release
SIMD: avx2_256
OpenMP: ON
CUDA: OFF
Root Cause:
The FahCore_a8 binary (compiled for kernel 4.15.0-128) is experiencing memory access violations (segfaults) when running on the modern kernel 6.14. The core is attempting to access invalid memory addresses, causing immediate crashes.
Troubleshooting steps attempted:
Fixed v7 to v8 config file migration issues (removed deprecated options: gpu, fold-anon, pci-bus, pci-slot)
Deleted and re-downloaded FahCore_a8 (rm -rf /var/lib/fah-client/cores/fahcore-a8*)
Full service restart
Tried multiple different CPU work units - all crash with identical symptoms
Verified no DNS/network issues (other computers on network fold successfully, GPU folding works)
Checked dmesg logs - confirmed segmentation faults in FahCore_a8
Workaround:
Currently running with CPU folding disabled (<cpus value="0"/> in config.xml). GPU folding continues to work flawlessly.
Question:
Is there a newer version of FahCore_a8 available that's compatible with Ubuntu 24.04 / kernel 6.14? Or is this a known issue with a planned fix?
The core appears to be nearly 4 years old (Jan 2021) and may need to be recompiled for modern Linux kernels.
FahCore_a8 v0.0.12 segfault on Ubuntu 24.04 LTS / Kernel 6.14 - CPU work units crash immediately
Moderators: Site Moderators, FAHC Science Team
-
- Posts: 1
- Joined: Fri Oct 17, 2025 9:20 pm
-
- Posts: 2101
- Joined: Sun Dec 16, 2007 6:22 pm
- Hardware configuration: 9950x, 9950x3D, 5950x, 5800x3D
7900xtx, RX9070, Radeon 7, 5700xt, 6900xt, Intel B580 - Location: London
- Contact:
Re: FahCore_a8 v0.0.12 segfault on Ubuntu 24.04 LTS / Kernel 6.14 - CPU work units crash immediately
There is nothing wrong with the core. Your CPU/system is unstable
Run full system stability test, like y-cruncher for extensive amount of time to determine if the system is stable or not. The way yours craps out straight away, it might be temperature of the cpu

Run full system stability test, like y-cruncher for extensive amount of time to determine if the system is stable or not. The way yours craps out straight away, it might be temperature of the cpu
